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    <title>结构伪类</title>

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        * {
            border: 2px solid blue;
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         :root {
            border-color: red;
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    <h3>结构伪类 :root</h3>

    <ul>
        <li>
            <span>川菜</span>
            <ul>
                <li>回锅肉</li>
                <li>盐煎肉</li>
            </ul>
        </li>
        <li>
            <span>湘菜</span>
            <ul>
                <li>毛血旺</li>
                <li>毛家豆腐</li>
            </ul>
        </li>
    </ul>

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